Surgical endoscopy is a surgical technique of using small-diameter long-handled tools such as graspers, forceps, scissors, retractors, dissectors and clamps specially designed to be inserted through small incisions in the skin (or other openings in the body) to perform operations within the body. The surgeon performing the surgery often cannot see the operation directly, and must watch the procedure on a video monitor fed by an endoscopic camera or endoscope. Endoscopic surgery replaces open surgery, which requires large incisions, essentially opening the body cavity completely, in order to perform surgery deep within the body. Endoscopic techniques have been used for gall stone removal, gall bladder removal, hernia repair, tumor removal, lymph node removal and appendectomy and many other operations. Endoscopic surgery is also called laparoscopic surgery, video assisted surgery, minimally invasive surgery, and band-aid surgery, but throughout this specification the term endoscopic surgery or laparoscopic surgery will be used.
In endoscopic surgery, a working space was created in the abdomen using the process called pneumoperitoneum or insufflation. Insufflation is the process of injecting gas into the body to blow it up like a balloon, creating a chamber filled with gas. When performed on the abdomen, the peritoneum is inflated and the procedure is known as pneumoperitoneum. The procedure can be used for inflating a space between the peritoneum and the skin to permit laparoscopic hernia repair, as illustrated in Keiturakis and Mollenauer, Apparatus and Method for Developing and Anatomic space for laparoscopic hernia repair, U.S. Pat. No. 5,496,345. Insufflation can be used also to inflate a tunnel shaped working space over a blood vessel, to facilitate blood vessel harvesting, as described in Fogarty, et al., Methods and Devices for Blood Vessel Harvesting, U.S. application Ser. No. 08/475,137, incorporated herein by reference. While the chamber is filled with gas, the surgeon inserts long slender laparoscopic tools through trocars and cannulas which pierce the skin and provide access ports into the insufflated chamber.
For abdominal surgery such as a cholecystectomy (gall bladder removal), the insufflation is accomplished by the following procedure. An incision is made at the lower edge of the belly button or umbilicus. The surgeon uses his fingers or a blunt dissection tool such as a blunt nosed obturator to uncover the fascia or abdominal muscles, then a large needle, referred to as a Verres needle is inserted into the abdomen or peritoneal cavity. The Verres needle punctures the fascia and peritoneum which cover the abdomen. A pressurized gas such as CO.sub.2, nitrous oxide or other suitable gas or liquid is injected into the abdomen through the needle, in effect inflating the abdomen like a balloon. After the abdomen is inflated, the Verres needle is removed. After the needle is removed, trocars and cannulas are inserted into the space created by the insufflation. Endoscopic instruments including an endoscope or laparoscope, scissors, graspers, etc., are inserted into the abdomen through the cannulas and manipulated to dissect tissue surrounding the gall bladder, remove the gall bladder, and stitch the internal wounds.
To harvest the saphenous vein using laparoscopic procedures, the surgeon may insufflate a tunnel shaped work space over a blood vessel. The tunnel is first created using obturators or tunneling devices or balloons inserted through small incisions along or over the saphenous vein. After the tunnel is created, the surgeon may insert skin seals and cannulas, and insufflation gas is injected through one of the trocars. While the tunnel is insufflated, the cannulas permit the surgeon to insert laparoscopic instruments into the tunnel to perform surgery on the saphenous vein.
The cannula used in the procedures described above is a length of rigid tube. The cannulas are typically about 6 inches or 15 centimeters long, and come in diameters matching various laparoscopic devices, generally from 2 to 15 mm. The trocars and cannula are designed to allow laparoscopic instruments to pass through them and prevent gas from escaping the abdomen or other insufflated work space. The cannula may have a flapper valve or a trumpet valve inside which opens to allow an endoscope or laparoscope or other instrument to pass through, and the valve closes against an access tube when the laparoscope is removed. A typical cannula flapper valve is illustrated in Stephens, et al., U.S. Pat. No. 5,197,955 entitled Universal Seal for Trocar Assembly. Some trocar/cannula devices also contain a duckbill valve to assist in sealing the trocar. A duckbill valve used to seal a cannula is illustrated in Kayan and Mollenauer, Cannula with Improved Valve and Skin Seal, U.S. Pat. No. 5,324,270. Another form of duckbill valve is illustrated in Durman, Self Sealing Flexible Elastomeric Valve and Trocar Assembly for Incorporating Same, U.S. Pat. No. 5,330,437, which refers to the duckbill valve as a self sealing valve. These references show the valves within rigid plastic housings.
The surgeon usually needs to place several trocars and cannulas into the insufflated workspace, and inserts as many as needed to accomplish the intended operation. If two or more cannulas are in place, the surgeon can view the procedure through any port, and can insert laparoscopic scissors, cutters and graspers and other tools through the cannulas in order to perform the surgery. Endoscopic and laparoscopic instruments of various designs are available, and they generally are about 5 to 12 mm in diameter (to match the inside bore of the cannulas) and about 10 to 40 cm in length. The tip of these endoscopic instruments may can a wide variety of working elements such as graspers, clip appliers, knot tying devices, scissors and snippers, electrocautery devices and more. Many of these instruments have structures at their tips which are of non-uniform diameter and odd or irregular shape, and these structures may catch or snag the flapper valve or duckbill valve upon withdrawal. When an instrument gets caught up on the valve, the surgeon must operate the valve handle to fully open the valve and allow the instrument to pass backwards out of the cannula. In the case of duckbill valves, no valve handle or operating mechanism is provided, so that excessive force may be required to pull the instrument backwards through the valve. The valve manipulation and excessive force are inconvenient, and may even require assistance from another surgeon. The valve manipulation and excessive force may also result in inadvertent removal of a cannula, further causing loss of insufflation pressure and possible injury to the patient as the insufflated work space collapses upon the tools and cannulas in place and as the cannula is re-installed into the body.